STM32G491CEU6 PWM output has a very fast rise time (~2ns) and 400mV Overshoot when not loaded. How come there is so much overshoot? Is this harmful for the pin?

BGheb.1 · ‎2021-09-10

I'm using PB14, TIM15_CH1 for my PWM signal. Since it's TT_a I/O structure 3.6V tolerant.

Tesla DeLorean · ‎2021-09-10

Perhaps you could ease back on the slew-rate setting? Perhaps from one of the 120-180 MHz ones to the 1-5 MHz, or something remotely appropriate..

GPIO_InitStruct.Speed = GPIO_SPEED_HIGH; // << THIS TO SPEED_LOW RATHER THAN SPEED_EXCESSIVELY_HIGH

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TDK · ‎2021-09-11

It could also be due to a poorly calibrated scope probe.

I doubt the chip can harm itself by generating a PWM with no/minimal attached circuitry.

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BGheb.1 · ‎2021-09-11

Thank you Tesla, I'll go ahead and try adjusting the slew rate and see if it helps with my issue.

BGheb.1 · ‎2021-09-11

But if find it really odd since I am also generating PWM from another pin and it has a slower rise time (~6ns) and little to no overshoot. I'm using the same code on both pins and probing with the same scope and same setup.

Uwe Bonnes · ‎2021-09-11

The overshoot is mostly from the connected device or from your probe connection. Try to reduce the GPIO speed...

S.Ma · ‎2021-09-12

Don t worry about this as there is no specific warning on the spec. RF modules, wifi or else do have a strong antenna output pin and in this case the spec does warn you that if the antenna is missing when transmitting, it is destructive to the pin.